Loads definitions from a directory of JSON files.

 Expected folder structure:
   /
   ├── agents/
   │   ├── my-agent.json
   │   └── research-agent.json
   ├── tools/
   │   ├── web-search.json
   │   └── calculator.json
   └── evals/
       ├── qa-suite.json
       └── coding-suite.json